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<-> XJ ANTITATIVE

ESTIMATION

constricted in
bustion tube
flasks are fitted

8.  A  spiral
reduced in
should be
and ready.
the spiral by
sufficient to \
and shake ofif

9.  A su
to fill the

blow-pipe flame, so that the end of the corn-
in as far as the constriction (Fig. 14).    The

3d corks.

copper gauze 15   cm. (6  in.) long, which is
alcohol as described on p. 12.    The spiral
just  before  use  when  the  tube is  filled
unnecessary to remove all the alcohol from
it in a current of carbon dioxide.    It is
it sharply through the air
excess of liquid.

giiantity of coarse copper oxide
tube two-thirds full and a

FIG. 14.

further quantity  of fine copper oxide to occupy
10—13 cm. (4-___£   In.) of the tube.
10.   Two   s/i.^z.llo'ii)   tin   dishes•,   ro—13   cm
(4—5 in.) in diameter for roasting copper oxide.
These dishes   oa-ra be obtained from.the iron-
monger in different sizes and are useful in the
laboratory for a, -v^ariety of purposes, such as for
oil, metal or sa/ncL-baths.
11.  A  squcz^tz    of copper gauze of moderate
mesh of the area,  of the tin dish.    It is turned
up at the edges    and is used for sifting the coarse from the
fine copper oxicle after each combustion.
12.  Pitre so^Zzzttn bicarboizate, NaHCO3, in powder free from
ammonia.
Filling th.0 Oombustion Tube.—A plug of asbestos is
first pushed in. fVom one end far enough to leave room for the
copper spiral? wliich should lie well within the furnace. This end
of the tube is subsequently attached to the azotometer and may
be called the /^o??t end. The coarse copper oxide is heated over
a Bunsen burntei- in one of the shallow tin dishes and the fine
oxide in anotlner. After about a quarter to half an hour the
burners are extinguished and the oxides whilst still warm are
introduced into their respective flasks with drawn-out necks,
The flasks are cl osed with corks and allowed to cool. The back
end of the combustion tube is now pushed horizontally into the
neck of the coarse oxide flask and the oxide poured on to the
plug by tilting- tlie flask and tube. The tube is filled with oxide
about two-thirds of its length. Into the flask containing the